Starting requires four things, fuel, spark, air, and compression. A starting problem is almost never lack of air or compression so focus on the first two. Did you turn on the petcock? Check for spark by pulling a plug, attaching it to its boot, grounding a metal side part or thread of the plug to the engine, and trying to start the bike. Make sure you are in neutral for this. Do this in a darker garage not in sunlight and you should see the spark. Try this for all four plugs.
So figure out if it is spark, fuel, or the unlikely something else. How about a vacuum leak like a cracked or disconnected vacuum hose preventing the petcock from working properly (petcock is vacuum activated). Will bike start with starter fluid/ether sprayed into carb? That would suggest problem is fuel related not spark related. You need to do further diagnosis. Focus first on determining if you are getting spark and fuel to cylinders.